Remove many features when building product mode

runtime/vm/flags.cc

Index: runtime/vm/flags.cc
diff --git a/runtime/vm/flags.cc b/runtime/vm/flags.cc
index e9bd84fbb4371a33de52de79545dbb0a813c4012..a2a63f7991020b81f566ea290f2fcb00acbbd34c 100644
--- a/runtime/vm/flags.cc
+++ b/runtime/vm/flags.cc
@@ -456,6 +456,9 @@ void Flags::PrintFlags() {
 
 
 void Flags::PrintFlagToJSONArray(JSONArray* jsarr, const Flag* flag) {
+  if (!FLAG_support_service) {
+    return;
+  }
   if (flag->IsUnrecognized() || flag->type_ == Flag::kFunc) {
     return;
   }
@@ -497,6 +500,9 @@ void Flags::PrintFlagToJSONArray(JSONArray* jsarr, const Flag* flag) {
 
 
 void Flags::PrintJSON(JSONStream* js) {
+  if (!FLAG_support_service) {
+    return;
+  }
   JSONObject jsobj(js);
   jsobj.AddProperty("type", "FlagList");
   JSONArray jsarr(&jsobj, "flags");